Drip irrigation emitters may be formed from several parts, such as an outer housing formed e.g. from two members. Drip emitters typically include an inlet through which liquid flowing in a pipe can enter the emitter and an outlet through which liquid that entered the emitter can exit to the outside environment. In addition drip emitters typically include liquid cavities such as an exit pool at a side of the emitter that is fitted to the pipe, a flow path formed at least in part of a flow restricting path, and a pressure regulating chamber.
The flow restricting path functions to control the rate at which liquid is discharged by the emitter and is normally referred to as a “labyrinth channel” or “labyrinth”. Through the flow restricting path liquid that enters the emitter must flow to reach the emitter outlet where it empties via the exit pool to the outside. The flow restricting path is a high resistance flow channel along which pressure of liquid flowing through the emitter drops relatively rapidly with distance along the path. Therefore, in some cases it may be advantageous to form the flow restricting path longer.
A resiliently flexible component often referred to as a membrane or diaphragm may be used in an emitter as part of the pressure regulating chamber to control the rate of liquid flowing out of the emitter, so that it is substantially independent of inlet pressure for a range of pressures typically encountered in irrigation applications which may be equal to a flow rate between about 0.4 and 12 liters per hour (1/h). The membrane is usually located between the inlet and the outlet and may contain at one side liquid that enters the emitter inlet to pass through the labyrinth and at the other side liquid that already passed through the labyrinth and reached a pressure regulating chamber that in some cases is located adjacent the emitter outlet.
The pressure regulating chamber typically has a wider cross section than the labyrinth emptying into it, in order to provide improved pressure regulating performance for the emitter. The membrane in response to increase in pressure of the entering liquid, may flex into the pressure regulating chamber to restrict the flow of liquid exiting the outlet and by that act to control the rate of liquid flowing out of the emitter.
Various types of connections may be used in order to retrain together parts of a drip irrigation emitter and in particular parts constituting outer housing members of the emitter. In addition, various considerations may be taken as to how to arrange the liquid cavities of the emitter one relative to the other in order to obtain an optimal design for the intended use and performance of the emitter.
U.S. Pat. No. 6,206,305 describes an emitter unit adapted to be integrally bonded to an internal surface of a pipe. The emitter has an outer housing, an inlet that communicates with an interior of the pipe; an outlet that communicates with an outlet of the pipe and a flow-restricting path. The housing is of closed box-like shape and includes a receiving member and a corresponding cover member. Projection and recess inter-engaging means formed on these members are adapted to form a close pressure fit to ensure effective retention between these members after assembly and prior to being bonded to a pipe. The emitter further includes a pressure regulating chamber and a flow restricting path located within the housing and an exit pool at an outer side of the housing where the emitter bonds to the pipe.
PCT publication WO2012137200 describes a drip emitter integrally installed within a pipe. The emitter has a body which at its side that is affixed to the internal wall of the pipe is formed with an exit pool that is elongated in its dimensions and substantially extends along the entire length of the body. The emitter in addition has at this side that attaches to the pipe a flow passage that circumferentially surrounds the elongated exit pool in order to impart to the emitter a symmetric configuration at the side connecting to the pipe and by that cancel the need for adjustment of orientation of the dripper before being fitted to a pipe.